High-temperature solar selective absorbers based on interface effects in refractory metals coated with transparent conductive oxides

At present, the utilization of thermal energy from sunlight has been widely adopted as the working principle of concentrated solar power (CSP) generation systems. In this research, we suggest a CSP technology based on the properties of transparent conductive oxide (TCO) thin films on metal substrates which is compatible with mass production of solar selective absorbers that can be utilized at high temperatures. Since the plasma wavelength of TCO materials is in the infrared region, electromagnetic waves with wavelengths longer than the plasma wavelength are reflected at the surface, whereas electromagnetic waves with shorter wavelengths pass through the surface layer and reach the substrate. In other words, a TCO thin film behaves as an antireflection film only in the transparency range of TCO coating. This phenomenon is demonstrated through numerical simulations based on rigorous coupled-wave analysis (RCWA). The prepared samples also show favorable spectral selectivity and satisfactory performance as solar selective absorbers, with a solar absorptance of 0.76, a thermal emittance of 0.12 at 800°C and a spectral selectivity of 6.5 at 800°C.